Honey, I smoked the discs!

[padonbike]

During a long descent in the Highlands with lightweight bikepacking gear on (approx +10kg) I got to the bottom of the descent and, as well as smelling, the dics pads were actually smoking!
I've never, ever had this happen before, indeed I thought it was just a myth.
I was using sintered pads in Shimano 105 disc brakes on my Pinnacle Arkose. I have done the descent many times before, but always on the gravel bike unloaded and generally going faster. This particular time, as well as carrying more weight in the bikepacking gear, I was descending more gingerly as I had come off the day before and was still battered in my upper body.
I always feel that the 105 brakes have considerably less power than the SLX on my MTB and I mainly put this down to the difference between 2 piston and 4 piston brakes.
Although the pads were fine after the smoking incident and do not appear to have visibly worn, I'm keen to avoid this happening again on future long descents, carrying weight and using these same slightly underpowered 105 brakes.
[As a side point: are GRX dedicated gravel brakes 2 piston or 4 piston? I'm assuming that they are more powerful than 105 road brakes, but still less powerful than XT, SLX etc MTB brakes?]
So after a lifetime of sintered pads on both MTB and more recently gravel bike, I've ordered ceramic pads, which the spiel seems to suggest may perform better. Also, I'm slightly reassured by the fact that they cost more.
Any experience as to whether brake-pimping via ceramic pads is a thing?

[GregMay]

How different was the ambient temperature? This will effect the disc cooling.

We’re you dragging the brake more than normal? This has a huge effect.

Personally, I’d opt for larger discs, and or, ones that cool faster over pads. The issue isn’t the pads generating the heat as such - but the discs getting rid of it.

[padonbike]

Thanks Greg. Temp in both cases was similar, around 20c. Yes was definitely dragging brake more than normal, especially towards bottom as steepness increased.
Good point about discs, although I'm not sure I can increase them with this set-up, hence looking down ceramic pad avenue.

[slarge]

Do the pads have the finned backplate that some shimano pads have? These are designed to get the heat away from the pad and prevent overheating. Dragging brakes is bad for heat generation- not sure if it helps but I try to alternate front and rear in some longer descents

[Bearbonesnorm]

Dragging brakes is bad for heat generation

Yep, even releasing them for a couple of seconds can help considerably.

[Jurassic]

I don't think the GRX calipers are very different, in fact I think they use the same pads (LO3A)? Definitely only two pot calipers anyway. IIRC the Hope calipers are 4 piston and work with GRX levers so not sure if they'd work with 105 as well. I've found my GRX brakes okay tbh and I run XT and Saint 4 pots on my mountain bikes but I did spec 160 rotors and adapters front and rear for the GRX stuff instead of the default 140s.

[padonbike]

Thanks people, some really useful replies. Although the descent was familiar, I was definitely taking it carefully this time because of sore ribs and using brakes a lot more, so I'll try to avoid this in future.
The pads are LO3A and I will look into the finned type in future - Uber do one but are out of stock at the moment.
Cheers

[Boab]

The pads are LO3A and I will look into the finned type in future

L03A are finned...!?! At least all the ones Ive had on my bike have been finned.



I've been trying to find somewhere with some in stock, at an acceptable price, as mine are wearing out. SwissStop do compatible pads, but they're even more expensive. Even the much cheap Gorrilla Brakes pads are all out of stock, unless you want sintered, they're not finned though.

[padonbike]

The pads are LO3A and I will look into the finned type in future

L03A are finned...!?! At least all the ones Ive had on my bike have been finned.



I've been trying to find somewhere with some in stock, at an acceptable price, as mine are wearing out. SwissStop do compatible pads, but they're even more expensive. Even the much cheap Gorrilla Brakes pads are all out of stock, unless you want sintered, they're not finned though.

Got mixed up with pad codes, I've looked at a lot last couple of days!
Yep, gorilla, disco, Uber all seem to be out of stock, especially of finned version of pads. Part of the reason I went for ceramic before they run out too!

[BigdummySteve]

Good brake modulation goes a long way but ultimately I decided that road bike brakes just don’t cut it off-road. I swapped out my sram red calipers for Hope RX4’s and have been happy with them for the last two years, I’ve saved the cost in disks and pads as the hopes seem to last a lot longer.
Shimano icetech disks also seem to help.

[jameso]

Good brake modulation goes a long way but ultimately I decided that road bike brakes just don’t cut it off-road

Agreed. Arkose goes ok off-road but additional 10kg load, the braking needed to stop the loaded bike running up speed and damaging tyre or rim, plus flat mount brakes with small pads and rotors.. seen quite a few riders in similar situations.
Big part of why I'm no fan of flat mounts on bikes that are intended to be loaded up properly.

As said already, best solution is a 180mm rotor but that's tricky on carbon fork and FM combo. Metal pads can generate a lot of heat but also put more of that heat into the brake/oil than resin pads which tend to heat the rotors. Worth sticking with metal but getting finned rotors for cooling.

You could also try some AM rotors with a deeper braking track also, road pads and rotors tend to be shallower/smaller than older MTB rotors. Think of the added depth as a cooling fin. That and finned pads might help fend off the overheating a bit longer.

[Scud]

Expensive upgrade, but if using SRAM or Shimano drop bar set up, i cannot recommend Hope RX4 callipers enough, so much more modulation and 4 piston calliper. I'm fairly heavy and with a fully loaded bike i can easily cook Shimano brakes even when i am trying to stay off the brakes as much as possible to dissipate heat. With the Hope, i can do 90 minute long descents, really gather some speed and still stop easily each and every time.

[padonbike]

Well thanks to everyone for the advice. 7 tough days with around 700kms including Torridon and Glen Affric and the brakes performed really well. Can't remember who, but the two key pieces of advice were:
1) manually ABS the brakes - momentarily releasing even on steep descents helped.
2) the original smoking may well have been caused by disc contamination, so set off with all brakes surfaces really clean.
I'd use ceramic pads but these wore out after 6 days of bone dry use and I switched back to sintered.
All in all, all good

[BigdummySteve]

Expensive upgrade, but if using SRAM or Shimano drop bar set up, i cannot recommend Hope RX4 callipers enough, so much more modulation and 4 piston calliper. I'm fairly heavy and with a fully loaded bike i can easily cook Shimano brakes even when i am trying to stay off the brakes as much as possible to dissipate heat. With the Hope, i can do 90 minute long descents, really gather some speed and still stop easily each and every time.

My experience exactly, apart from the cost. I’ve saved a boat load of cash on pads and disk replacements since I fitted mine back in May 2019.

[redefined_cycles]

Just came across this thread and thought to ask... Are Shimano Zee meant to be anywhere near as good as the Hope RX4... Just thinking of the price difference when I eventually come to fit out my bike. I imagine the Zees would be much cheaper but think they're only twin pot...